Much of the infrastructure that supports the smooth operation of our society (bridges, roads, and the like) is old and is in need of critical repair. Due to the lack of real-time monitoring of critical conditions, such as strain, humidity, and corrosion, accidents have occurred in the past, such as the bridge collapse in Montreal, Canada in 2006 or the bridge collapse in Minneapolis, Minn. in 2007. Such accidents cost precious life, time, and financial resources. Vigorous discussions and activities are taking place both in terms of monitoring the status of existing bridges as well as what to do with future bridges and infrastructure that are yet to be built. If new innovative solutions are not developed, future cost to maintain any newly built infrastructure will be staggering.
At present, a great deal of research activity is ongoing in the sensors front. Sensing systems and sensor networks are geared to the real-time health monitoring of existing bridges. Many of these techniques involve plug-and-play solutions of existing techniques. For example, a strain sensor is embedded inside the concrete which measures the strain in the steel reinforcement. The measured data is then transferred using a wire to an outside wireless transceiver which then sends all data to a host computer for further analysis and processing. The cost and complexity of cabling is very high. Besides, wiring is prone to damage itself due to corrosion resulting from water and chloride ingress. Major advantages of wireless sensors over traditional wired sensors are their low cost and ease of installation. Furthermore, wireless embedded sensors have improved reliability over conventional wired sensors since the presence of wires within an infrastructure creates the possibility of loss of connection due to crack and corrosion resulting from changes in their surrounding environment.
Conventional radio frequency identification device (RFID) sensors typically only operate when a reader sends a signal to energize such RFID sensors.
As such, improved sensors are desirable. Methods related to such sensors would be particularly beneficial.